Waste minimizing paper dispenser

ABSTRACT

A paper dispenser including a carriage that is rotatable between at least a first orientation and a second orientation. The carriage holds at least two rolls of paper. In the first orientation, the first roll is in a primary position and the second roll is in a secondary position. In the second orientation, the first roll is in the secondary position and the second roll is in the primary position. A roll sensor senses the amount of paper remaining on the roll held in the primary position. Paper from at least one of the two rolls is fed into a feed mechanism for dispensation. A transfer mechanism feeds paper from the roll held in the secondary position into the feed mechanism when the roll sensor senses that the paper on the roll held in the primary position is depleted to less than a predetermined diameter.

PRIORITY

The present application is a continuation of U.S. patent applicationSer. No. 09/780,733 filed Feb. 9, 2001, now U.S. Pat. No. 6,592,067, thedisclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the present invention is paper dispensers. In particulardispensers which dispense paper stored on rolls.

2. Background

As is readily apparent, a long-standing problem is to keep paper towelsavailable in a dispenser and at the same time use up each roll ascompletely as possible to avoid paper waste. As part of this system, oneought to keep in mind the person who refills the towel dispenser. Anoptimal solution would make it as easy as possible and as “fool-proof”as possible to operate the towel refill system and have it operate insuch a manner as the least amount of waste of paper towel occurs. Thiswaste may take the form of “stub” rolls of paper towel not being usedup.

Transfer devices are used on some roll towel dispensers as a means ofreducing waste and decreasing operating costs. These transfer deviceswork in a variety of ways. The more efficient of these devicesautomatically begin feeding from a reserve roll once the initial roll isexhausted. These devices eliminate the waste caused by a maintenanceperson when replacing small rolls with fresh rolls in an effort toprevent the dispenser from running out of paper. These transfer devices,however, tend to be difficult to load and/or to operate. Consequently,these transfer devices are less frequently used, even though they arepresent.

The current transfer bar mechanisms tend to require the maintenanceperson to remove any unwanted core tube(s), remove the initial partialroll from the reserve position, and position the initial partial rollinto the now vacant stub roll position. This procedure is relativelylong and difficult, partly because the stub roll positions in thesecurrent paper towel dispensers tend to be cramped and difficult to getto.

In order to keep a roll available in the dispenser, it is necessary toprovide for a refill before the roll is used up. This factor generallyrequires that a “refill” be done before the current paper towel roll isused up. If the person refilling the dispenser comes too late, the papertowel roll will be used up. If the refill occurs too soon, the amount ofpaper towel in the almost used-up roll, the “stub” roll, will be wastedunless there is a method and a mechanism for using up the stub roll eventhough the dispenser has been refilled. Another issue exists, as to theease in which the new refill roll is added to the paper towel dispenser.The goal is to bring “on-stream” the new refill roll as the last of thestub roll towel is being used up. If it is a task easily done by theperson replenishing the dispensers, then a higher probability existsthat the stub roll paper towel will actually be used up and also that arefill roll be placed into service before the stub roll has entirelybeen used up. It would be extremely desirable to have a paper toweldispenser which tended to minimize paper wastage by operating in anearly “fool proof” manner with respect to refilling and using up thestub roll.

As an enhancement and further development of a system for deliveringpaper towel to the end user in as cost effective manner and in auser-friendly manner as possible, an automatic means for dispensing thepaper towel is desirable, making it unnecessary for a user to physicallytouch a knob or a lever.

SUMMARY OF THE INVENTION

The present invention is directed towards a waste minimizing paperdispenser. A rotatable carriage includes first and second roll holdersadapted to hold first and second rolls of paper, respectively. Thecarriage is rotatable between first and second orientations. In thefirst orientation, the first roll of paper is held in a primary positionand the second roll of paper is held in a secondary position. In thesecond orientation, the first roll of paper is held in a secondaryposition and the second roll of paper is held in the primary position.Paper from at least one of the two rolls is fed into a feed mechanismfor dispensation. A roll sensor detects the amount of paper on the rollheld in the primary position. Paper on the roll held in the secondaryposition is held in a transfer mechanism. When the paper on the rollheld in the primary position is reduced to less than a predetermineddiameter, the transfer mechanism feeds paper from the roll held in thesecondary position into the feed mechanism. Thereafter, paper from bothrolls is dispensed until one of the two rolls is exhausted.

During operation, when the roll held in the primary position isexhausted, the carriage may be rotated to move the roll held in thesecondary position into primary position. Alternatively, the carriage ina smaller dispenser may be adapted to rotate the roll held in thesecondary position into the primary position when that roll is depletedto less than a predetermined diameter.

Accordingly, it is an object of the present invention to provide animproved paper towel dispenser. Other objects and advantages will appearhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, wherein likereference numerals refer to similar components:

FIG. 1 is a side elevation of the dispenser with the cover closed, withno internal mechanisms visible;

FIG. 2 is a perspective view of the dispenser with the cover closed,with no internal mechanisms visible;

FIG. 3 shows a view of the carousel support, the locking bar and thetransfer bar;

FIG. 4A is a perspective view of the of the dispenser with the carouseland transfer bar, fully loaded with a main roll and a stub roll;

FIG. 4B is a side view of the locking bar showing the placement of thecompression springs;

FIG. 4C shows the locking mechanism where the locking bar closest to therear of the casing is adapted to fit into a mating structure in the rearcasing;

FIG. 5 is a perspective, exploded view of the carousel assembly;

FIG. 6A is a side elevation view of the paper feeding from the stub rollwhile the tail of the main roll is positioned beneath the transfer bar;

FIG. 6B is a side elevation view of the stub roll is completelyexhausted, so that the transfer bar tucks the tail of the main roll intothe feed mechanism;

FIG. 7A is a side elevation view of the carousel ready for loading whenthe main roll reaches a specific diameter;

FIG. 7B is a side elevation view of the locking bar being pulledforwardly to allow the carousel to rotate 180°, placing the main roll inthe previous stub roll position;

FIG. 7C shows the extension springs which tend to maintain the transferbar legs in contact with the stub roll;

FIG. 7D shows the cleanable floor of the dispenser;

FIG. 8A shows a schematic of the proximity circuit;

FIG. 8B (prior art) shows the schematic for the National Semiconductordual comparator LM393;

FIG. 9A shows the square wave output at U1A, pin 1;

FIG. 9B shows the RC exponential waveforms at pins 5; and

FIG. 9C shows the RC exponential waveforms at pin 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description is of the best mode presently contemplated forcarrying out the invention. This description is not to be taken in alimiting sense, but is merely made for the purpose of describing thegeneral principles of the invention. The scope of the invention shouldbe determined with reference to the claims.

An embodiment of the invention comprises a carousel-based dispensingsystem with a transfer bar for paper towels, which acts to minimizeactual wastage of paper towels. As an enhancement and furtherdevelopment of a system for delivering paper towel to the end user in acost effective manner and in as user-friendly manner as possible, anautomatic means for dispensing the paper towel is desirable, making itunnecessary for a user to physically touch a knob or a lever. Anelectronic proximity sensor is included as part of the paper toweldispenser. A person can approach the paper towel dispenser, extend hisor her hand, and have the proximity sensor detect the presence of thehand. The embodiment of the invention as shown here, is a system, whichadvantageously uses a minimal number of parts for both the mechanicalstructure and for the electronic unit. It has, therefore, an enhancedreliability and maintainability, both of which contribute to costeffectiveness.

An embodiment of the invention comprises a carousel-based dispensingsystem with a transfer bar for paper towels, which acts to minimizeactual wastage of paper towels. The transfer bar coupled with thecarousel system is easy to load by a service person; consequently itwill tend to be used, allowing stub rolls to be fully utilized. Insummary, the carousel assembly-transfer bar comprises two components, acarousel assembly and a transfer bar. The carousel rotates a used-upstub roll to an up position where it can easily be replaced with a fullroll. At the same time the former main roll which has been used up suchthat its diameter is less than some p inches, where p is a rationalnumber, is rotated down into the stub roll position. The tail of the newmain roll in the upper position is tucked under the “bar” part of thetransfer bar. As the stub roll is used up, the transfer bar moves downunder spring loading until the tail of the main roll is engaged betweenthe feed roller and the nib roller. The carousel assembly is symmetricalabout a horizontal axis. A locking bar is pulled out to unlock thecarousel assembly and allow it to rotate about its axis, and is thenreleased under its spring loading to again lock the carousel assembly inplace.

A side view, FIG. 1, of the dispenser 20 with the cover 22 in placeshows an upper circular bulge 24, providing room for a full roll ofpaper towel, installed in the upper position of the carousel. The shapeof the dispenser is such that the front cover tapers inwardly towardsthe bottom to provide a smaller dispenser volume at the bottom wherethere is a smaller stub roll of paper towel. The shape tends to minimizethe overall size of the dispenser. FIG. 2 shows a perspective view ofthe dispenser 20 with cover 22 in place and the circular (cylindrical)bulge 24, together with the sunrise-like setback 26 on the cover 22,which tends to visually guide a hand toward the pseudo-button 28,leading to activation of a proximity sensor (not shown). A lightemitting diode (LED) 130 is located centrally to the pseudo-button 28.The LED 130 (FIG. 3) serves as an indication that the dispenser 20 ison, and dispensing towel. The LED 130 may be off while the dispenser isnot dispensing. Alternatively, the LED 130 may be lit (on), and when thedispenser 20 is operating, the LED 130 might flash. The LED 130 mightshow green when the dispenser 20 is ready to dispense, and flashinggreen, or orange, when the dispenser 20 is operating to dispense. Anysimilar combination may be used. The least power consumption is wherethe LED 130 only lights during a dispensing duty cycle. The sunrise-likesetback 26 (FIG. 2) allows a hand to come more closely to the proximitysensor (not shown).

FIG. 3 shows the main elements of the carousel assembly 30. The carouselarms 32 have friction reducing rotating paper towel roll hubs 34, whichare disposed into the holes of a paper towel roll (66, 68, FIG. 4A). Thelocking bar 36 serves to lock and to release the carousel for rotationabout its axis 38. The locking bar 36 rides on one of the correspondingbars 40. The two corresponding bars 40 serve as support bars.Cross-members 42 serve as stiffeners for the carousel assembly 30 andalso serve as paper guides for the paper to be drawn over and down tothe feed roller 50 and out the dispenser 20. These cross members areattached in a rigid fashion to the corresponding bars 40 and in thisembodiment do not rotate.

The legs 46 of the transfer bar 44 do not rest against the frictionreducing rotating paper towel roll hubs 34 when there is no stub roll 68present but are disposed inward of the roll hubs 34. The bar part 88 ofthe transfer bar 44 will rest against a structure of the dispenser, forexample, the top of modular electronics unit 132, when no stub roll 68is present. The bar part 88 of the transfer bar 44 acts to bring thetail of a new main roll of paper towel 66 (FIG. 4A) down to the feedroller 50 which includes intermediate bosses 146 (FIG. 3) and shaft 144.The carousel assembly is disposed within the fixed casing 48. The coveris not shown.

Feed roller 50 serves to feed the paper towels 66, 68 (FIG. 4A) beingdispensed onto the curved dispensing ribs 52. The curved dispensing ribs52 are curved and have a low area of contact with the paper toweldispensed (not shown). If the dispenser 20 gets wet, the curveddispensing ribs 46 help in dispensing the paper towel to get dispensedby providing low friction and by holding the dispensing towel off of thewet surfaces it would otherwise contact.

The feed roller 50 is typically as wide as the paper roll, and includesdrive rollers 142 and intermediate bosses 146 on the drive shaft 144.The working drive rollers or drive bosses 142 (FIG. 3) are typically aninch or less in width, with intermediate bosses 146 (FIG. 3) locatedbetween them. Intermediate bosses 146 are slightly less in diameter thanthe drive rollers or drive bosses 142, having a diameter 0.015 to 0.045inches less than the drive rollers or drive bosses 142. In thisembodiment, the diameter of the intermediate bosses 146 is 0.030 inchesless than the drive roller 142. This configuration of drive rollers ordrive bosses 142 and intermediate bosses 146 tends to prevent thedispensing paper towel from becoming wrinkled as it passes through thedrive mechanism and reduces friction, requiring less power to operatethe feed roller 50.

A control unit 54 operates a motor 56. Batteries 58 supply power to themotor 56. A motor 56 may be positioned next to the batteries 58. A light60, for example, a light-emitting diode (LED), may be incorporated intoa low battery warning such that the light 60 turns on when the batteryvoltage is lower than a predetermined level.

The cover 22 of the dispenser is preferably transparent so that theamount of the main roll used (see below) may be inspected, but also sothat the battery low light 60 may easily be seen. Otherwise anindividual window on an opaque cover 22 would need to be provided toview the low battery light 60. Another approach might be to lead out thelight by way of a fiber optic light pipe to a transparent window in thecover 22.

In a waterproof version of the dispenser, a thin piece of foam rubberrope is disposed within a u-shaped groove of the tongue-in-groove matingsurfaces of the cover 22 and the casing 48. The dispensing shelf 62 is amodular component, which is removable from the dispenser 20. In thewaterproof version of the dispenser 20, the dispensing shelf 62 with themolded turning ribs 52 is removed. By removing the modular component,dispensing shelf 62, there is less likelihood of water being divertedinto the dispenser 20 by the dispensing shelf 62, acting as a funnel orchute should a water hose or spray be directed at the dispenser 20, bythe shelf and wetting the paper towel. The paper towel is dispensedstraight downward. A most likely need for a waterproof version of thedispenser is where a dispenser is located in an area subject to beingcleaned by being hosed down. The dispenser 20 has an on-off switch whichgoes to an off state when the cover 22 is pivoted downwardly. The actualswitch is located on the lower face of the nodule 54 and is not shown.

In one embodiment, the user may actuate the dispensing of a paper towelby placing a hand in the dispenser's field of sensitivity. There can beadjustable delay lengths between activations of the sensor.

There is another aspect of the presence of water on or near thedispenser 20. A proximity sensor (not visible) is more fully discussedbelow, including the details of its operation. However, as can beappreciated, the sensor detects changes of capacitance such as arecaused by the introduction of an object with a high dielectric constantrelative to air, such as water, as well as a hand which is about 70%water. An on-off switch 140 is provided which may be turned off beforehosing down and may be turned on manually, afterwards. The switch 140may also work such that it turns itself back on after a period of time,automatically. The switch 140 may operate in both modes, according tomode(s) chosen by the user.

A separate “jog” off-on switch 64 is provided so that a maintenanceperson can thread the paper towel 66 by holding a spring loaded jogswitch 64 which provides a temporary movement of the feed roller 50.

FIG. 4A shows the dispenser case 48 with the carousel assembly 30 andtransfer bar 44. The carousel assembly 30 is fully loaded with a mainroll 66 in the secondary position and a stub roll 68 in the primaryposition, both mounted on the carousel arms 32 to rotate on the rotatingreduced friction paper towel roll hubs 34 (only shown from the back ofthe carousel arms 32). In the carousel assembly 30, the two carouselarms 32, joined by corresponding bars 40 and cross members 42, rotate incarousel fashion about a horizontal axis defined by the carouselassembly rotation hubs 38. The locking bar 36 is supported, or carried,by a corresponding bar 40. The corresponding bar 40 provides structuralrigidity and support. The locking bar 36 principally serves as a lockingmechanism. Each paper towel roll 66, 68 has an inner cardboard tubewhich acts as a central winding core element, and which provides in ahole in paper towel roll 66, 68 at each end for engaging the hubs 34.

FIG. 5 shows the carousel assembly 30 in exploded, perspective view. Thenumber of parts comprising this assembly is small. From a reliabilitypoint of view, the reliability is increased. From a manufacturing pointof view, the ease of manufacture is thereby increased and the cost ofmanufacture is reduced. The material of manufacture is not limitedexcept as to the requirements of cost, ease of manufacture, reliability,strength and other requirements imposed by the maker, demand.

When the main roll, 66 (FIG. 4A) and the stub roll 68, (FIG. 4A) are inplace, the carousel arms 32 are connected by these rolls 66 and 68 (FIG.4A). Placing cross-members 42 to connect the carousel arms 32 with thelocking 36 and corresponding 40 bar results in better structuralstability, with racking prevented. The locking bar 36, which was shownas a single unit locking bar 36 in the previous figures, acts as alocking bar 36 to lock the carousel assembly 30 in the properorientation. It acts also as the release bar, which when released,allows the carousel assembly 30 to rotate. Two compression springs 70,72 are utilized to center the locking bar 36.

FIG. 4B is a side view of the locking bar showing the placement of thecompression springs. The compression springs 70, 72 also tend to resistthe release of the locking bar 36, insuring that a required force isneeded to unlock the locking bar 36. The required force is typicallybetween 0.5 lbf and 3.0 lbf, or more. In this embodiment, the force is2.0 lbf when the spring in a fully compressed position, and 1.1 lbf whenthe spring is in the rest position. In the rest position, the forces ofthe opposing springs offset each other.

The actual locking occurs as shown in FIG. 4C. The locking bar 36closest to the rear of the casing 48 is adapted to fit into a generallyunshaped mating structure 118 which is adapted to hold the locking bar36 and prevent it and the carousel assembly 30 from rotating. When thelocking bar 36 is pulled away from the rear of the casing 48, thelocking bar 36 is disengaged from the mating structure 118. The matingstructure has an upper “high” side 120 and a lower “low” side 122, wherethe low side has a “ramp” 124 on its lower side. As the locking bar 36is pulled out to clear the high side 120, the carousel assembly 30 isfree to rotate such that the top of the carousel assembly 30 rotates upand away from the back of the casing 48. As the carousel assembly 30begins to rotate, the user releases the locking bar 36 which, under theinfluence of symmetrically placed compression springs 70, 72 returns toits rest position. As the carousel assembly rotates, the end of thesymmetrical locking bar 36 which originally was disposed toward the usernow rotates and contacts the ramp 124. A locking bar spring, e.g., 70 or72, is compressed as the end of the locking bar 36 contacting the ramp124 now moves up the ramp 124. The end of the locking bar 36 is pressedinto the space between the low side 122 and the high side 120, as theend of the locking bar 36 slides past the low side 122. A lockedposition for the carousel assembly 30 is now reestablished.

FIG. 5 shows the carousel arms 32 adapted to receive the loading of anew roll of towel 66 (FIG. 4A). The arms 32 are slightly flexible andbent outward a small amount when inserting a paper towel roll 66 (FIG.4A) between two opposite carousel arms 32. A friction reducing rotatingpaper towel roll hub 34 is inserted into a hole of a paper towel roll 66(FIG. 4A), such that one roll hub 34 is inserted into a hole on eachside of the paper towel roll 66 (FIG. 4A). Also shown in FIG. 5 are thetamper resistant fasteners 74, which attach the friction-reducingrotating paper towel roll hubs 34 to the carousel arms 32.

FIG. 5 shows the surface 76 of the roll hubs 34 and the surface 78 ofthe carousel arms 66, which contact each other. These contact surfaces76, 78 may be made of a more frictionless material than that of whichthe carousel arms 32 and the roll hubs 34 are made. For example, aplastic such as polytetrafluoroethylene (PTFE), e.g., TEFLON®, may beused, as a thin layer on each of the contacting surfaces. The papertowel dispenser 20 and its components may be made of, including but notlimited to, plastic, metal, an organic material which may include but isnot limited to wood, cardboard, treated or untreated, a combination ofthese materials, and other materials for batteries, paint, if any, andwaterproofing.

FIG. 6A shows the paper 80 feeding from the stub roll 68 while the tail82 of the main roll 66 is positioned beneath the transfer bar 44. Thelegs (visible leg 46, other leg not shown) of the transfer bar 44 restsagainst the stub roll. When the diameter of the stub roll 68 is largerby a number of winds of paper towel than the inner roll 84, the legs 46of the transfer bar 44 dispose the bar 88 of the transfer bar 44 to berotated upward from the feed roller 50.

FIG. 6B shows the situation where the stub roll 68 is exhausted, so thatthe transfer bar 44 tucks the tail 82 of the main roll 66 into the feedmechanism 86. FIG. 6B shows the stub roll 68 position empty, as the stubroll has been used up. The stub roll core 84 is still in place. As thestub roll 68 is used up, the legs 46 of the transfer bar 44 move uptoward the stub roll core (inner roll) 84, and the bar 88 of thetransfer bar is disposed downward toward the feed roller 50 and towardthe top of a structural unit of the dispenser 20 (FIG. 2), such as thetop of the electronics module 132 (FIG. 3). Initially the main roll 66is in reserve, and its tail 82 in an “idling” position such that it isunder the transfer bar 44. The main roll 66 and its tail 82 are notinitially in a “drive” position. However, as the stub roll 68 is usedup, the downward motion of the bar transfer bar, 44 driven by its springloading, brings the bar 88 of the transfer bar 44 down to engage themain roll tail 82 with the feed roller 50.

FIG. 7A shows the carousel assembly 30 ready for loading when the mainroll 66 reaches a specific diameter. The diameter of the main roll 66may be measured by comparison of that diameter with the widened “ear”shape 122 (FIG. 4A) on each end of the carousel arms 32. That part ofeach carousel arm 32 is made to measure a critical diameter of a mainroll 66. The carousel assembly 30 is tilted forward when it is locked.The carousel assembly 30 may rotate unassisted after the locking bar 36is released, due to the top-heavy nature of the top roll. That is, thetorque produced by the gravitational pull on the main-roll 66 is largerthan that needed to overcome friction and the counter-torque produced bythe now empty stub roll 68.

FIG. 7B shows the process of loading where the service person pulls thelocking bar 36 and allows the carousel to rotate 180°, placing the mainroll 66 in the previous stub roll 68 position. Now a new full sized roll66 can be loaded onto the main roll 66 position. The transfer bar 44automatically resets itself. The transfer bar 44 is spring loaded so asto be disposed with the transfer bar legs 46 pressed upward against thestub roll 68 or the stub roll core 84. The transfer bar legs 46 areadapted to be disposed inward of the roll hubs 34 so the bar 88 of thetransfer bar 44 will have a positive stop at a more rigid location, inthis case, the top of the electronics module 132 (FIG. 2).

FIG. 7C shows the extension springs 126, 128 which tend to maintain thetransfer bar legs 46 in contact with the stub roll 68 or stub roll core84.

The transfer bar 44 contains the two extension springs 126, 128. Thespring forces are typically 0.05 lbf to 0.5 lbf in the bar 44 loweredposition and 0.2 lbf to 1.0 lbf in the bar 44 raised position. In thisembodiment, the spring forces are 0.2 lbf in the lowered position an0.43 lbf in the raised position. The force of the two springs 126, 128is additive so that the transfer bar 44 is subject to a total springforce of 0.4 lbf in the lowered position and 0.86 lbf in the raisedposition.

While modular units (FIG. 7D) such as the electronics module 132, themotor 56 module, and the battery case 150, are removable, they fit, or“snap” together so that the top of the electronics unit 132, the top ofthe motor 56 module and remaining elements of the “floor” 148 of thedispensing unit 20 form a smooth, cleanable surface. Paper dust anddebris tend to accumulate on the floor 148 of the dispenser 20. It isimportant that the dispenser 20 is able to be easily cleaned as part ofthe maintenance procedure. A quick wiping with a damp cloth will sweepout and pick up any undesirable accumulation. The removable modulardispensing shelf 64 may be removed for rinsing or wiping.

The feed roller 50 may be driven by a motor 56 which in turn may bedriven by a battery or batteries 58, driven off a 100 or 220V AC hookup,or driven off 20 a transformer which is run off an AC circuit. Thebatteries may be non-rechargeable or rechargeable. Rechargeablebatteries may include, but not be limited to, lithium ion, metalhydride, metal-air, nonmetal-air. The rechargeable batteries may berecharged by, but not limited to, AC electromagnetic induction or lightenergy using photocells.

A feed roller 50 serves to feed the paper towel being dispensed onto thecurved dispensing ribs 52. A gear train (not visible) may be placedunder housing 86, (FIG. 3) for driving the feed roller. A control unit54 (FIG. 3) for a motor 56 (FIG. 3) may be utilized. A proximity sensor(not shown) or a hand-operated switch 64 may serve to turn the motor 56on and off.

As an enhancement and further development of a system for deliveringpaper towel to the end user in as cost effective manner anduser-friendly manner as possible. An automatic means for dispensing thepaper towel is desirable, making it unnecessary for a user to physicallytouch a knob or a lever. Therefore, a more hygienic dispenser ispresent. This dispenser will contribute to less transfer of matter,whether dirt or bacteria, from one user to the next. The results ofwashing ones hands will tend to be preserved and hygiene increased.

An electronic proximity sensor is included as part of the paper toweldispenser. A person can approach the paper towel dispenser, extend hisor her hand, and have the proximity sensor detect the presence of thehand. Upon detection of the hand, a motor is energized which dispensesthe paper towel. It has long been known that the insertion of an objectwith a dielectric constant into a volume with an electromagnetic fieldwill tend to modify the properties, which the electromagnetic fieldsees. The property of the hand, a dielectric constant close to that ofwater, is enough to alter the net capacitance of a suitable detectorcircuit.

An embodiment of the invention comprises a balanced bridge circuit. SeeFIG. 8A. The component U1A 90 is a comparator (TLC3702 158) configuredas an oscillator. The frequency of oscillation of this component, U1A90, of the circuit may be considered arbitrary and non-critical, as faras the operation of the circuit is concerned. The period of theoscillator is set by the elements Cref 92, Rhys 94, the trim resistance,Rtrim 96, where the trim resistance may be varied and the rangeresistors Rrange 152 are fixed. The resistors Rrange 152 allow limits tobe placed-on the range of adjustment, resulting in an easier adjustment.The adjustment band is narrowed, since only part of the total resistancethere can be varied. Consequently a single potentiometer may be used,simplifying the adjustment of Rtrim 96. A value for Rrange 152 for theschematic shown in FIG. 8A might be 100 kΩ. Rtrim 96 might have anadjustment range of 10 kΩ to 50 kΩ. The output signal at pin 1 98 ofcomponent U1A 90 is a square wave, as shown in FIG. 9A. Cref 92 ischarged by the output along with ANT 100, both sustaining theoscillation and measuring the capacitance of the adjacent free space.The signals resulting from the charging action are applied to a secondcomparator, U1B 102, at pins 5 104 and 6 106 (FIG. 8A). These signalsappear as exponential waveforms, as shown in FIG. 9B and FIG. 9C.

The simplest form of a comparator is a high-gain differential amplifier,made either with transistors or with an op-amp. The op-amp goes intopositive or negative saturation according to the difference of the inputvoltages because the voltage gain is typically larger than 100,000, theinputs will have to be equal to within a fraction of a millivolt inorder for the output not to be completely saturated. Although anordinary op-amp can be used as comparator, there are special integratedcircuits intended for this use. These include the LM 306, LM311, LM393154 (FIG. 8A), LM393V, NE627 and TLC3702 158. The LM393V is a lowervoltage derivative of the LM393 154. The LM393 154 is an integratedcircuit containing two comparators. The TLC3702 158 is a micropower dualcomparitor with CMOS push-pull 156 outputs. FIG. 8B (prior art) is aschematic which shows the different output structures for the LM393 andthe TLC3702. The dedicated comparators are much faster than the ordinaryop-amps.

The output signal at pin 1 98 of component U1A 90, e.g., a TL3702 158,is a square wave, as shown in FIG. 2A. Two waveforms are generated atthe inputs of the second comparator, U2B 102. The first comparator 90 isrunning as an oscillator producing a square-wave clocking signal, whichis input, to the clock input of the flip-flop U2A 108, which may be, forexample, a Motorola D flip-flop, No. 14013.

Running the first comparator as a Schmitt trigger oscillator, the firstcomparator U1A 90 is setup to have positive feedback to thenon-inverting input, terminal 3 110. The positive feedback insures arapid output transition, regardless of the speed of the input waveform.Rhys 94 is chosen to produce the required hysteresis, together with thebias resistors Rbias1 112 and Rbias2 114. When these two bias resistors,Rbias1 112, Rbias2 114 and the hysteresis resistor, Rhys 94, are equal,the resulting threshold levels are ⅓ V+ and ⅔V+, where V+158 is thesupply voltage. The actual values are not especially critical, exceptthat the three resistors Rbias1 112, Rbias2 114 and Rhys 94, should beequal, for proper balance.

The value of 294 kΩ maybe used for these three resistors, in theschematic shown in FIG. 8A.

An external pullup resistor, Rpullup1 116, which may have a value, forexample, of 470 Ω, is only necessary if an open collector, comparatorsuch as an LM393 154 is used. That comparator 154 acts as anopen-collector output with a ground-coupled emitter. For low powerconsumption, better performance is achieved with a CMOS comparator,e.g., TLC3702, which utilizes a cmos push-pull output 156. The signal atterminal 3 110 of U1A charges a capacitor Cref 92 and also charges anANT sensor 100 with a capacitance which Cref 92 is designed toapproximate. A value for Cref for the schematic of FIG. 8A, for the mostcurrent board design, upon which it depends, is about 10 pF. As theclocking square wave is effectively integrated by Cref 92 and thecapacitance of ANT 100, two exponential signals appear at terminals 5104 and 6 106 of the second comparator U1B, through the Rprotect 160static protection resistors. Rprotect 160 resistors provide limitingresistance which enhances the inherent static protection of a comparitorinput lines, particularly for the case of pin 5 104 of U1B 102. In theschematic shown in FIG. 8A, a typical value for Rprotect 160 might be 2kΩ. One of the two exponential waveforms will be greater, depending uponthe settings of the adjustable resistance Rtrim 96, Cref 92, and ANT100. The comparator U1B 102 resolves small differences, reporting logiclevels at its output, pin 7 118. As the waveforms may initially be setup, based on a capacitance at ANT 100 of a given amount. However, uponthe intrusion of a hand, for example, into the detection field of theantenna ANT 100, the capacitance of ANT 100 is increased significantlyand the prior relationship of the waveforms, which were set with ANT 100with a lower capacitance, are switched over. Therefore, the logic leveloutput at pin 7 118 is changed and the d flip-flop 108 state is changedvia the input on pin 5 of the D flip-flop 108.

The second comparator 102 provides a digital quality signal to the Dflip-flop 108. The D flip-flop, U2A 108, latches and holds the output ofthe comparator U1B 90. In this manner, the second comparator is reallydoing analog-to-digital conversion. A suitable D flip-flop is a Motorola14013.

The presence, and then the absence, of a hand can be used to start amotorized mechanism on a paper towel dispenser, for example. Anembodiment of the proximity detector uses a single wire or a combinationof wire and copper foil tape that is shaped to form a detection field.This system is very tolerant of non-conductive items, such as papertowels, placed in the field. A hand is conductive and attached to a muchlarger conductor to free space. Bringing a hand near the antenna servesto increase the antenna's apparent capacitance to free space, forcingdetection.

The shape and placement of the proximity detector's antenna (FIG. 8A,100) turns out to be of some importance in making the proximity sensorwork correctly. Experimentation showed that a suitable location wastoward the lower front of the dispenser unit. The antenna (FIG. 8A, 100)was run about two-thirds the length of the dispensing unit, in amodular, replaceable unit above the removable dispensing shelf 62 (FIG.3). This modular unit would be denoted on FIG. 3 as 120.

A detection by the proximity detection circuit (FIG. 8A) in the module120 sets up a motor control flip flop so that the removal of the handwill trigger the start of the motor cycle. The end of the cycle isdetected by means of a limit switch which, when closed, causes a resetof the flip-flop and stops the motor. A cycle may also be initiated byclosing a manual switch.

A wide range of sensitivity can be obtained by varying the geometry ofthe antenna and coordinating the reference capacitor. Small antennaehave short ranges suitable for non-contact pushbuttons. A large antennacould be disposed as a doorway-sized people detector. Another factor insensitivity is the element applied as Rtrim. If Rtrim 96 is replaced byan adjustable inductor, the exponential signals become resonant signalswith phase characteristics very strongly influenced by capacitivechanges. Accordingly, trimming with inductors may be used to increaserange and sensitivity. Finally, circuitry may be added to the antenna100 to improve range and directionality. As a class, these circuits aretermed “guards” or “guarding electrodes,” old in the art, a type ofshield driven at equal potential to the antenna. Equal potential insuresno charge exchange, effectively blinding the guarded area of the antennarendering it directional.

The antenna design and trimming arrangement for the paper toweldispenser application is chosen for adequate range and minimum cost. Theadvantages of using a guarded antenna and an adjustable inductor arethat the sensing unit to be made smaller.

From a safety standpoint, the circuit is designed so that a detectionwill hold the motor control flip-flop in reset, thereby stopping themechanism. The cycle can then begin again after detection ends.

The dispenser has additional switches on the control module 54. FIG. 3shows a “length-of-towel-to-dispense-at-one-time”(“length”) switch 134.This switch 134, is important in controlling how long a length of papertowel is dispensed, for each dispensation of towel. It is an importantsetting for the owner of the dispenser on a day-to-day basis indetermining cost (to the owner) versus the comfort (to the user) ofgetting a large piece of paper towel at one time.

A somewhat similar second switch 136 is“time-delay-before-can-activate-the-dispensing-ofanother-paper-towel”(“time-delay”) switch 136. The longer the time delayis set, the less likely a user will wait for many multiple towels todispense. This tends to save costs to the owner. Shortening the delaytends to be more comfortable to a user.

A third switch 138 is the sensitivity setting for the detection circuit.This sensitivity setting varies the resistance of Rtrim 96 (FIG. 8A).Once an effective antenna 100 (FIG. 8A) configuration is set up, thedistance from the dispenser may be varied. Typical actual use mayrequire a sensitivity out to one or two inches, rather than four or sixinches. This is to avoid unwanted dispensing of paper towel. In ahospital setting, or physicians office, the sensitivity setting might bemade fairly low so as to avoid unwanted paper towel dispensing. At aparticular work location, on the other hand, the sensitivity might beset fairly high, so that paper towel will be dispensed very easily.

While it is well known in the art how to make these switches accordingto the desired functionalities, this switch triad may increase theusefulness of the embodiment of this invention. The system, as shown inthe embodiment herein, has properties of lowering costs, improvinghygiene, improving ease of operation and ease of maintenance. Thisembodiment of the invention is designed to consume low power, compatiblewith a battery or battery pack operation. In this embodiment, a 6 voltDC supply is utilized. A battery eliminator may be use for continuousoperation in a fixed location. There is a passive battery supply monitorthat will turn on an LED indicator if the input voltage falls below aspecified voltage.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. Moreover, thescope of the present application is not intended to be limited to theparticular embodiments of the process, machine, manufacture, compositionof matter, means, methods and steps described in the specification. Asone of ordinary skill in the art will readily appreciate from thedisclosure of the present invention, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present invention.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

What is claimed is:
 1. A paper towel dispenser comprising: a carriagerotatable between at least a first orientation and a second orientation,the carriage comprising: a first roll holder adapted to hold a firstroll of paper in a primary position when the carriage is in the firstorientation and in a secondary position when the carriage is in thesecond orientation; and a second roll holder adapted to hold a secondroll of paper in the secondary position when the carriage is in thefirst orientation and in the primary position when the carriage is inthe second orientation; a roll sensor for sensing the amount of paperremaining on the roll held in the primary position; a feed mechanisminto which paper from at least one of the two rolls is fed fordispensation; and a transfer mechanism adapted to feed paper from theroll held in the secondary position into the feed mechanism when theroll sensor senses that the paper on the roll held in the primaryposition is depleted to less than a first predetermined diameter,thereby causing dispensation of paper from both rolls.
 2. The papertowel dispenser of claim 1, wherein the carriage is rotatable to movethe roll held in the secondary position into the primary position whenthe roll held in the primary position is exhausted.
 3. The paper toweldispenser of claim 2, wherein the carriage is rotatable to move the rollheld in the secondary position into the primary position when the rollheld in the secondary position is depleted to less than a secondpredetermined diameter.
 4. The paper towel dispenser of claim 1, whereinthe carriage rotates about a central axis, and the roll holders aredisposed equidistant from and on opposite sides of the central axis. 5.The paper towel dispenser of claim 4, wherein the carriage furtherincludes two parallel paper guides, the paper guides being disposed onopposite sides of and equidistant from the central axis and on a lineapproximately halfway between the two roll holders.
 6. The paper toweldispenser of claim 1, wherein for each of the two carriage orientations,the roll held in the secondary position is approximately verticallyaligned with the roll in the primary position.
 7. The paper toweldispenser of claim 1, wherein for each of the two carriage orientations,the roll held in the secondary position is offset from verticalalignment with the roll in the primary position by approximately 5degrees.
 8. The paper towel dispenser of claim 1 further comprising ahousing which encloses the carriage, the roll sensor, the feedmechanism, and the transfer mechanism, the housing including an ejectionport through which the dispenser mechanism dispenses the paper.
 9. Thepaper towel dispenser of claim 8, the carriage further including a leverarm and the housing further including a catch, wherein the lever armengages the catch to maintain the rotation orientation of the carriage.10. The paper towel dispenser of claim 9, wherein the lever arm isradially slidable and centrally biased on the carriage.
 11. The papertowel dispenser of claim 8, wherein the ejection port includes aplurality of ribs.
 12. The paper towel dispenser of claim 1, wherein theroll sensor is integral to the transfer mechanism.
 13. The paper toweldispenser of claim 1, wherein the feed mechanism dispenses paper inpredetermined lengths.
 14. The paper towel dispenser of claim 13,wherein the feed mechanism is motor driven.
 15. The paper toweldispenser of claim 14, wherein the feed mechanism includes a proximitydetector which defines a proximity field, wherein the proximity detectoris adapted to activate the motor driven feed mechanism when a user'shand is within the proximity field.
 16. The paper towel dispenser ofclaim 1 further comprising means of visually determining the amount ofpaper remaining on the roll held in the secondary position.
 17. A papertowel dispenser comprising: a rotatable carriage comprising: a firstroll holder adapted to hold a first roll of paper; and a second rollholder adapted to hold a second roll of paper; wherein the carriage isrotatable between at least a first rotation orientation in which thefirst roll holder holds the first roll in a primary position and thesecond roll holder holds the second roll in a secondary position, and asecond rotation orientation in which the first roll holder holds thefirst roll in the secondary position and the second roll holder holdsthe second roll in the primary position; a roll sensor for sensing theamount of paper remaining on the roll held in the primary position; afeed mechanism into which paper from at least one of the two rolls isfed for dispensation; and a transfer mechanism, wherein when the rollsensor senses that the paper on the roll held in the primary position isdepleted to less than a first predetermined diameter, the transfermechanism feeds paper from the roll held in the secondary position intothe feed mechanism, thereby causing dispensation of paper from bothrolls; wherein the carriage is rotatable to move the roll held in thesecondary position into the primary position when paper from the rollheld in the secondary position is fed into the feed mechanism.
 18. Thepaper towel dispenser of claim 17, wherein the carriage rotates about acentral axis, and the roll holders are disposed equidistant from and onopposite sides of the central axis.
 19. The paper towel dispenser ofclaim 18, wherein the carriage further includes two parallel paperguides, the paper guides being disposed on opposite sides of andequidistant from the central axis and on a line approximately halfwaybetween the two roll holders.
 20. The paper towel dispenser of claim 17,wherein for each of the two carriage orientations, the roll held in thesecondary position is approximately vertically aligned with the roll inthe primary position.
 21. The paper towel dispenser of claim 17, whereinfor each of the two carriage orientations, the roll held in thesecondary position is offset from vertical alignment with the roll inthe primary position by approximately 5 degrees.
 22. The paper toweldispenser of claim 17 further comprising a housing which encloses thecarriage, the roll sensor, the feed mechanism, and the transfermechanism, the housing including an ejection port through which thedispenser mechanism dispenses the paper.
 23. The paper towel dispenserof claim 22, the carriage further including a lever arm and the housingfurther including a catch, wherein the lever arm engages the catch tomaintain the rotation orientation of the carriage.
 24. The paper toweldispenser of claim 23, wherein the lever arm is radially slidable andcentrally biased on the carriage.
 25. The paper towel dispenser of claim22, wherein the ejection port includes a plurality of ribs.
 26. Thepaper towel dispenser of claim 17, wherein the roll sensor is integralto the transfer mechanism.
 27. The paper towel dispenser of claim 17,wherein the feed mechanism dispenses paper in predetermined lengths. 28.The paper towel dispenser of claim 27, wherein the feed mechanism ismotor driven.
 29. The paper towel dispenser of claim 28, wherein thefeed mechanism includes a proximity detector which defines a proximityfield, wherein the proximity detector is adapted to activate the motordriven feed mechanism when a user's hand is within the proximity field.30. The paper towel dispenser of claim 17 further comprising means ofvisually determining the amount of paper remaining on the roll held inthe secondary position.
 31. The paper towel dispenser of claim 17,wherein the carriage is rotatable to move the roll held in the secondaryposition into the primary position when the roll held in the primaryposition is exhausted.
 32. The paper towel dispenser of claim 31,wherein the carriage is rotatable to move the roll held in the secondaryposition into the primary position when the roll held in the secondaryposition is depleted to less than a second predetermined diameter.
 33. Apaper towel dispenser comprising: a housing; a carriage disposed withinthe housing, the carriage being rotatable about a central axis andcomprising: a first roll holder adapted to hold a first roll of paper; asecond roll holder adapted to hold a second roll of paper, the secondroll holder being disposed equidistant from the central axis and on anopposite side of the central axis from the first roll holder; and aradially aligned lever arm adapted to engage a catch disposed on thehousing to maintain the carriage in one of two orientations, wherein inthe first orientation, the first roll holder holds the first roll in aprimary position and the second roll holder holds the second roll in asecondary position, and in the second orientation the first roll holderholds the first roll in the secondary position and the second rollholder holds the second roll in the primary position, and wherein ineach orientation the roll held in the secondary position is offset fromvertical alignment with the roll in the primary position byapproximately 5 degrees; a feed mechanism disposed within the housing,wherein paper from at least one of the two rolls is fed into the feedmechanism for dispensation through a paper feed opening in the housing;and a transfer mechanism disposed within the housing, the transfermechanism comprising a roll sensor adapted to sense the amount of paperremaining on the roll held in the primary position, wherein when theroll sensor senses that the paper on the roll held in the primaryposition is depleted to less than a first predetermined diameter, thetransfer mechanism feeds paper from the roll held in the secondaryposition into the feed mechanism, thereby causing dispensation of paperfrom both rolls until the paper on the roll held in the primary positionis exhausted, wherein the carriage is rotatable to move the roll held inthe secondary position into the primary position when the roll held inthe primary position is exhausted and when the roll held in thesecondary position is depleted to less than a second predetermineddiameter.
 34. A method of dispensing paper towels comprising:maintaining a rotatable carriage in a first orientation, the rotatablecarriage comprising a first roll holder adapted to hold a first roll ofpaper and a second roll holder adapted to hold a second roll of paper,wherein in the first orientation the first roll is held in a primaryposition and the second roll is held in a secondary position; feedingpaper from the first roll into a feed mechanism for dispensation;sensing when paper on the first roll is depleted to less than apredetermined diameter; automatically feeding the paper from the secondroll into the feed mechanism when the paper on the first roll isdepleted to less than a first predetermined diameter such that paperfrom both rolls is dispensed until the paper on the first roll isexhausted; and rotating the carriage to a second orientation, wherein inthe second orientation the second roll is held in the primary position.35. The method of claim 34, wherein rotating the carriage to a secondorientation includes rotating the carriage when the paper on the firstroll is exhausted.
 36. The method of claim 35, wherein rotating thecarriage to a second orientation includes rotating the carriage when thepaper on the second roll is depleted to less than a second predetermineddiameter.
 37. The method of claim 34 further comprising placing a thirdroll of paper in the first roll holder after the first roll isexhausted.
 38. The method of claim 34 further comprising feeding thepaper from the second roll into a transfer mechanism, whereinautomatically feeding the paper from the second roll into the feedmechanism includes activating the transfer mechanism to feed the paperfrom the second roll into the feed mechanism when the paper on the firstroll is depleted to less than a predetermined diameter.
 39. A method ofdispensing paper towels comprising: maintaining a rotatable carriage ina first orientation, the rotatable carriage comprising a first rollholder adapted to hold a first roll of paper and a second roll holderadapted to hold a second roll of paper, wherein in the first orientationthe first roll is held in a primary position and the second roll is heldin a secondary position; feeding paper from the first roll into a feedmechanism for dispensation; feeding the paper from the second roll intoa transfer mechanism; sensing when paper on the first roll is depletedto less than a predetermined diameter; activating the transfer mechanismto automatically feed the paper from the second roll into the feedmechanism when the paper on the first roll is depleted to less than apredetermined diameter such that paper from both rolls is dispensed;rotating the carriage to a second orientation when the paper on thefirst roll is exhausted, wherein in the second orientation the secondroll is held in the primary position; and placing a third roll of paperin the first roll holder.
 40. The method of claim 39, wherein rotatingthe carriage to a second orientation includes rotating the carriage whenthe paper on the second roll is depleted to less than a secondpredetermined diameter.